Method of operating a jet propulsion motor



.s cums ic -s l -o application relates 'to jet propulsion motors, and particularly to-methods for improving their 'efliciency by the provision of certain novel propellants il-"fuels for such motors, 'This application is a division of copending application Serial No. 284,442, filed April 25, 1952, whichis a continuation-impart of application Serial No. 539,030, filed June 6, 1944, 'now US. Patent No; 2,645,079 V I Jet propulsion motors may be defined, for the purposes of this invention, asmotors which derive their driving power tromthe escape through, a jet or nozzle of'the relatively large volume of products resulting from the combustion of a fuel by means of an oxidizing agent. The gas jet may be exhaustedinto the open air as in the rocket type of motor, or it may be trained on a movable pieceof machinery such" as the blades of a fan inthe turbine-type of motor. I V 1 The primary requisites of the propellants used in such motors are that they should be safe to handle, stable in storage, should' ignite. readily and positively, and "burn rapidly and smoothly, with a maximum volume of 'prod-' ucts ofcombustion. It is ordinarily preferable to'oxidize' the fuel only to the point where a maximum amount of power is produced per unit weight of oxidizer. This may involveeithe'r complete or partial oxidation of the fuel.

. It is an'object of'this invention to supply novel fuels,

and novel fuel-oxidizer combinations for jet propulsion motors, whereby their simplicity of construction and efficiency of operation are increased.

1t is lsnown that certain classes of organic compounds which contain a polar-group, for example, aniline, are more readily oxidizable, i.e., have a lower ignition temperature thanrnost of the straight hydrocarbon Thisinvention concerns the employment of certain classes of polar compounds as jet fuels which are even more advantageous from the standpoint of ease of oxidation and gas volume production than the previously proposed fuels-containing polar groups. The fuels disclosed herein may be employed alone or in'combination with hydro carbon fuels such as petroleum distillates, or they may be mixed with other fuels and/or with an oxidizer.

. All of the fuels described herein, except these containing active oxygen as hereinafterdefined, require the use of" extraneous oxidizing materials for their combustion, i.e. they are not monopropellants. The oxidizers which may be employed include nitric acid, oxygen, and nitrous oxide (these three being preferred), or air, ozone, hydroperoxides, metal peroxides, metal manganates, permanganates, chlorates, perchlorates, hypochlorates, persulfates, chromites,chromates, bichromates and the like, as well as sulfur, the halogens such as fluorine, chlorine,

States atent nitrogen dioxide is very suitable, and red fumingv nitric acid containing up toa'bo'ut 20% by weight of nitrogen dioxide and less than 5% of water is also excellent, although as indicated fuming nitric acid of greater than 95% concentration is preferred; Any nitric acid having a concentration greater than about 80% may be employed. Liquid nitrogen dioxide may also be employed as well as other oxides of nitrogen.

In cases Where the fuel and the oxidizer are compatible with each other at normal temperatures, they may be compounded together in the desired proportions and stored in a single tank or compartment for transfer to the combustion chamber. In this case the combus-' tion chamber must be provided with an igniter such as a spark plug or detonating' device; In case the mixture of fuel and oxidizer is a solid or semisolid composition, and is therefore not readily transferred from the storage compartmentto the combustion chamber, the fuel andthe oxidizer may-"be blended or intimately mixed andpositioned in the combustion chamber itself in such a posi tion that there is no danger of its obstructingithe' 'jet. Thus, a mixture of asphalt and potassium perchlorate,

for example, may be heated sufiiciently to allow it, to be poured intothe combustion chamber so that it will solidify at the opposite end of the combustion chamber from the jet. It is desirable that when such a mixture is burned, it willburn smoothly at the surface of the bromine and gi'odine "and-theircompounds with oxygen,

nitrogen and sulfur. Nitro compounds such as nitromethanemay also be employed as well as liquid hydrogen peroxide. If nitric acid'is employed it is preferable to use fumingnitric acid containing less than about 5% by weight of water. White fuming nitric acid containing less than about 2% of water and substantially no charge and not burn in a series of explosions. The additives of this invention aid materially in making the com bust-ion of such a fuel smoother, and in permitting ignition at lower temperatures. 1 J

Where either the fuel or the oxidizer is a solid and the other component of the propellant is a fluid the solid material may be positioned in the combustion chamber as described'above and the fluid material charged into 'thecombustion chamber from a separate tank or compartnient. The proportion of the oxidizer, compared to the fuel in the propellant employed is preferably somewhat less than the amount theoretically required for complete combustion. Generally, proportions between about 50% and about of the amount of oxidizer by weight fequired'for complete combustion are satisfactory, al-

though higher or lower proportions may be necessary in' some instances. ,7 In those cases where the fuel and oxidizing material are not compatible with each other, is. where the materials. will spontaneously ignite upon admixture, it is necessary to provide separate compartments for each component, and each must be separately transferred to' the combustion chamber. In this case both components are ordinarily liquids, gases or fluid suspensions andthe transfer is accomplished by pressuring each chamber with a piston gas such asnitrogen or "other inert gas to force the fuel and oxidizer into the combustion chamber. In

this case a separate igniting device is ordinarily not I required in the combustion chamber, the fuel igniting spontaneously upon admixture with the oxidizer. Oxidizers which seldom require an ignition device include, for example, hydrogen peroxide, oxygen, nitric acid, and ozone.

The materials which are employed herein either as fuels or as additives to other fuels consist broadly of the highly polar organic nitrogen containing compounds selected from the group consisting of amine oxides,

nitriles, imines and ox-imes. These materials may be designated by the following general form'ulaet.

Nitriles RCN- I Imines R=NR Amine oxides RsNO an organic radical or hydrogen.

The organic radicals in the-above'formulae may vary: over a wide range. They may include paraflinic, olefinic,

aromatic, naphthenic, or acetylenic residues, and may contain in addition one or more other functional groups. Specific examples of suitable. compounds which may be employed include the following: 7

I. NITRILES CHaC-N CHFCHCN O-GN acetonitrile acrylonitrile benzonitrile II. AMINE OXIDES CH2 (CHa)N-"- (O):N=O OIL =O trtmethylamine oxide triphenyl amine oxide dimethyl phenylamine oxide III. IMINES 3 HzC-CH2 =NH (CHa)iC=NH- NH cyciohexyllmina isopropylitnine ethyleneimine 1v. oxnvras =NOH t CH=NOH CHaCH=NOH cyolohesanoneoxime benzaldoxime acetaldoxime CHsC-CC.Ha (CHaNOH);

HON NOH dhnethyl glyoxime trimerie tormaldoxlme Many other examples could be cited of compounds similar to the above which are suitable for use as fuels in this invention. In general, homologs, isomers, and substituted derivatives may be employed. ,The compounds may also contain more than one of the particu-. lar functional groups illustrated in the above examples. If substituted compounds are employed, those containing nitro, nitrate, nitrite, nitroso, chloro, bromo, amino, carbonyl, hydroxyl, diazo, azine, hydrazine, and similar substituents, in addition to the particular polar groups illustrated, may be advantageously employed.

The blended jet propulsion fuels of this invention may be prepared by adding the above described materials to another liquid fuel which is either a solvent or a suspending medium for the additive. v The preferred fuels employed in such blended mixtures are petroleum gasoline fractions, although higher liquid fractions such as gas oil, kerosene and even lubricating oil fractions, gas fractions such as natural gas or liquefied gas fractions, and

even solid or semi-solid fractions may be employed such as petroleum, parafiin wax and asphalt fractions. The additive may be employed in amounts preferably between about 1% and about 10%, although amounts as low as one-hundredth of a percent are efiective in some instances and amounts as high as may be employed to advantage in other instances Combinations of difi'erent additives may be employed, and where necessary, as in cases where the additive is insoluble in hydrocarbons, various oxygenated compounds may be employed to alter the solvent capacity of the hydrocarbon fuel. Examples of suitable mutual solvents for the additive and the hydrocarbon include alcohols such as methyl, ethyl or isopropyl, alcohol, acetone, dioxane, and aldehydes.

When the above compounds are employed in conjunction with hydrocarbon fuels, it is generally preferred to use those compounds having a high ratio of polar groups to carbon atoms. Specifically it is preferred to employ those compounds containing not more than about four carbon atoms for each polar functional group. Converse- 13/, when the above fuels are employed without an added hydrocarbon fuel or solvent it is preferred that the hydrocarbon component should be relatively larger. Specifically it is preferred that the compounds should contain more than about four carbon atoms for each functional group.

at the end opposite from the jet.

Any of the above materials may be employed as fuels or fuel additives by one or more of the procedures in the following examples. These examples should, however, be considered as illustrative only and not limiting.

Example I A liquid fuel is prepared by dissolving 10% by volume of acetonitrile in about 90% of a paraflinic crude gasoline fraction having a boiling range of about 100 F. to 400 F., and containing less than about 10% of aromatic type hydrocarbons. This fuel may be charged into one feed tank of a jet propulsion motor and pressured with nitrogen to about 1500 pounds per square inch. A second feed tank may be charged with fuming nitric acid and similarly pressured with nitrogen. The fuel and the nitric acid oxidizer may then be released from the fuel tanks and fed to a combustion chamber where they are allowed to react spontaneously. This reaction is an oxidation reaction or combustion and the hot gaseous products pass out through a jet in order to provide driving force. For a jet combustion chamber of about cubic inches in size, the rate of fuel injection may be about 2 pounds for every 3% pounds of oxidizer. The effect of the acetonitrile in the above fuel is to lower the ignition temperature below that of the gasoline alone, and to make theburning smooth and noncxplosive, thus providing a smooththrust during the entire period of operation rather than asingle explosion or a series of explosive bursts. Similar effects are obtained when any of the above described fuels are added to hydrocarbon fuels.

Example II A suitable solid propellant for these purposes may be compounded for example from about 20% trimeric formaldoxime, 40% potassium chlorate, and about 40% of a high melting asphalt. ,To, compound the mixture form-aldoxime and the potassium chlorate are mixed together and the melted asphalt is stirred into the mixture. The semi-fluid mass may then be poured into the combustion chamber of the jet engine and allowed to solidify The material may be combusted when desired by providing a spark ignition near the surface of the mixture, or by a suitable detonating device.

Example 111 Another suitable fuel may consist of about 20% ethylene imine dissolved in about ethyl alcohol. This mixture may suitably becombusted with an oxidizer consisting of hydrogen peroxide which is admitted from a separate storage tank to the combustion chamber. The mixture formed in the combustion chamber will ignite spontaneously.

The invention is not limited to the particular conditions described in the above examples, since different pressures, up to several thousand pounds per square inch, different rates of introduction of fuels and oxidizers, generally increasing'with the combustion pressure and the size of the motor, and different sizes'and styles of equipment may be employed. The fuels of this particular invention are effective in any type of jet propulsion motor to increase the certainty, the smoothness and the efficiency of the combustion.

Modifications of this invention which would occur to one skilled in the art are to be included in the invention as defined in the following claims.

We claim:

l. In a method of operating a jet propulsion motor wherein a fuel is burned in a combustion chamber, with a proportion of added oxidizer at least about 50% of the amount required for complete combustion of said fuel, and the products of combustion are allowed to escape through a jet thereby producing a driving force, said oxidizer being selected from the group consisting of oxygen, nitric acid, nitrous oxide and hydrogen peroxide, the improvement which comprises employing therein as 5 a fuel a composition consisting of a substantial proportion, at least about 1% by volume, of an organic nitrogen compound selected from the group consisting ofacetonitrile, acrylonitrile, benzonitrile, trimethylamine oxide, triphenylamine oxide, N,N limethyl phenylarnine oxide, cyclohexylimine, isopropylimine, cyclohexanone oxime, benzaldoxime, acetaldoxime, dimethyl glyoxime, and trimeric formaldoxime, any remaining component of said 'fuel consisting essentially of a combustible solvent selected from the group consisting of hydrocarbons, lower aliphatic alcohols, and mixtures thereof.

2. In a method of operating a jet propulsion motorwherein a fuel is burned in a combustion chamber with a proportion of added oxidizer at least about 50% of the amount required for complete combustion of said' fuel, and the products of combustion are allowed to escape through a jet thereby producing a driving force, said oxidizer being selected from the group consisting of oxygen, nitric acid, nitrous oxide, and hydrogen peroxide, the

improvement which comprises employing therein as a 20 fuel a liquid mixture of a combustible solvent and between about 1% and 50% by volume of an organic nitrogen compound selected from the group consisting of acetonit-rile, acrylonitrile, benzonitrile, trimethylamine oxide, triphenylamine oxide, N,N-dimethyl phenylamine oxide, cyclohexylimine, isopropylimine, cyclohexanone oxime, benzaldoxime, acetaldoxime, dimethyl glyoxime,

and tn'meric formaldoxime, said combustible solvent be ing selected from the group consisting of hydrocarbons,

References Cited in the file of this patent UNITED STATES PATENTS 2,573,471 Malina. et al. Oct 30, 1951 2,682,336 Moberly June 29, 1954 2,824,791 Osborg Feb. 25, 1958 OTHER REFERENCES 25 Da Rosa: Journal of the American Rocket Society, No.

61, March 1945, pages 4, 5, 6 and 15, copy in Scientific Lib. 

1. IN A METHOD OF OPERATING A JET PROPULSION MOTOR WHEREIN A FUEL IS BURNED IN A COMBUSTION CHAMBER WITH A PROPORTION OF ADDED OXIDIZER AT LEAST ABOUT 50% OF THE AMOUNT REQUIRED FOR COMPLETE COMBUSTION OF SAID FUEL, AND THE PRODUCTS OF COMBUSTION ARE ALLOWED TO ESCAPE THROUGH A JET THEREBY PRODUCING A DRIVING FORCE, SAID OXIDIZER BEING SELECTED FROM THE GROUP CONSISTING OF OXYGEN, NITRIC ACID, NITROUS OXIDE AND HYDROGEN PEROXIDE, THE IMPROVEMENT WHICH COMPRISES EMPLOYING THEREIN AS A FUEL A COMPOSITION CONSISTING OF A SUBSTANTIAL PROPORTION, AT LEAST ABOUT 1% BY VOLUME, OF AN ORGANIC NITROGEN COMPOUND SELECTED FROM THE GROUP CONSISTING OF ACETONITRILE, ACRYLONITRILE, BENZONITRILE, TRIMETHYLAMINE OXIDE, TRIPHENYLAMINE OXIDE, N,N-DIMETHYL PHENYLAMINE OXIDE, CYCLOHEXYLIMINE, ISOPROPYLIMINE, CYCLOHEXANONE OXIME, BENZALDOXIME, ACETALDOXIME, DIMETHYL GLYOXIME, AND TRIMERIC FORMALDOXIME, ANY REMAINING COMPONENT OF SAID FUEL CONSISTING ESSENTIALLY OF A COMBUSTIBLE SOLVENT SELECTED FROM THE GROUP CONSISTING OF HYDROCARBONS, LOWER ALIPHATIC ALCOHOLS, AND MIXTURES THEREOF. 